Small articles such as springs, fasteners, twist drills and the like have traditionally and conventionally been heat treated by placing the articles in a perforated metal box and placing the box in a furnace into which heated air or other gas is introduced or by placing the articles in a rotating drum provided with heated air or other gas in the interior thereof.
Such articles or devices (especially springs and many fasteners) are often characterized by a tendency to become entangled when placed helter skelter into a container. Normally hand labor is required to separate such devices which have been heat treated in bulk in the manner of the prior art and generally an excessive and even stupendous cost factor is thereby added to the overall cost of producing the part. For example, it has been not uncommon for the cost of carrying out this single step in the manufacture of a spring to outweigh or be larger than the total of all other costs in the manufacture of the spring, including cost of materials, cost of original manufacture of the spring, all costs of transportation and even the cost of installing the spring in the final device for which it is destined which can often be done automatically by robot-type machinery. That which is true for such springs is also true for many other metal wire parts and spring steel fasteners and fastener parts.
Generally throughout the remainer of this specification reference will be had to springs. But it is to be understood that such reference to springs is intended to include other small articles or parts to which the invention may apply, including for example but not limited to spring steel fasteners, spring steel fastener parts, twist drills, bifurcated rivets and hollow rivets, the heat treating of which is required as a step in the manufacture thereof.
The device of the present invention is normally adapted to be located immediately adjacent a spring coiler, that is, a spring manufacturing machine, so that as each spring manufactured by the spring coiler is ejected from the coiler or falls from the coiler it is introduced by gravity or by the force of the ejection from the machine into the device of the invention.
In the device of the invention at least one tube (usually two tubes) is provided in which the springs travel vertically downward or at an angle downwardly. The tube is preferably straight and cylindrical but for parts other than coil springs may have any other suitable configuration. Springs form a column or stack of springs within the tube of the device, the lowermost spring being supported by a release mechanism provided at the lower extremity of the device and the remainder of the springs in the column or stack being supported by one another. The release mechanism releases a spring from the bottom of the heat treating device of the invention for each spring introduced at the top of the device so that the rate of release of the springs from the heat treating device exactly corresponds to the rate of introduction of the springs to the heat treating device.
Generally the springs travel downwardly through a tube of the device due to the force of gravity acting thereon but in certain instances, generally in those instances wherein the tube is relatively long and inclined at a relatively small angle to the horizontal, means to vibrate the tube or to vibrate the entire device and thereby vibrate the tube may be provided to assist gravitational force to cause the springs to travel downwardly therethrough.